1. Field of the Invention
The present invention relates to a method of producing a chitosan scaffold having high tensile strength and a chitosan scaffold produced using the method.
2. Description of the Related Art
Chitosan is a linear amino polysaccharide having β-D-glucosamine (2-amino-2-deoxy-β-D-glucan) repeating units that are linked to each other via a (1→4) linkage. Chitosan can be prepared, for example, by deacetylating chitin with alkali. Chitosan is generally characterized by the degree of deacetylation, and is dissolved not in water, but in most of the acidic mediums having pH levels at or lower than 6.9.
Conventionally, there are various methods of preparing a scaffold for culturing cells using chitosan as a based material. For example, Korean Patent No. 0375422 discloses a porous bead-type matrix for cell culture having relatively uniform pores having a size in the range of 30 to 150 μm on the surface of and inside the matrix, wherein a material that is used to form the porous bead-type matrix is chitosan, water-soluble chitosan, or a mixture thereof, and cells to be cultured are attached to and grow on the surface of the matrix or the pore inside the matrix. In this case, a method of preparing porous chitosan beads for culturing cells includes preparing one of a chitosan solution by dissolving chitosan in an aqueous acetic acid solution, a water-soluble chitosan solution by dissolving water-soluble chitosan in deionized water, or a mixture of the chitosan solution and the water-soluble chitosan solution, adding the solution drop wise to an organic solvent at a low temperature in the range of −65 to −5° C. to obtain beads, and freeze-drying the chitosan beads. Korean Patent No. 0546793 also discloses a method of preparing a foam dressing using chitosan including: obtaining a chitosan structure as foam dressing by freeze-drying an aqueous acidic solution of chitosan having glycerol; completely removing an acid by neutralizing and washing the chitosan structure sequentially with a 95% or higher pure ethanol, a 70% or higher ethanol solution, a 50% or higher ethanol solution, and water or a buffer solution; and freeze-drying the neutralized chitosan structure.
In a porous scaffold that is used in tissue engineering and cell culture, various elements, such as elements used to attach cells to the porous scaffold, essential ingredients used to culture the attached cells, and metabolites resulted from cell growth, need to flow into and out of the porous scaffold. Examples of such elements may include cytokine, hormones, and medium ingredients. Cells or tissues in addition to various elements should easily flow into the porous scaffold and be easily attached to the porous scaffold for the cell or tissue growth. Thus, the porous scaffold needs to have a size distribution of pores providing conditions proper for cell inflow, attachment and growth, such as proper surface area, and facility in supplying oxygen and nutrients. For this, the porous scaffold needs to have excellent interconnectivity between pores.
However, according to such conventional technologies, pores in inner walls of the chitosan structure are formed in tubal shapes due to film-forming ability of the chitosan. Thus, the chitosan structure has disadvantages of not having high tensile strength or having nonuniform pore size. Particularly, when the porous scaffold has a pore size of 120 μm or greater, cells are not easily attached to the porous scaffold and pass through the pores during cell inoculation to attach cells to the porous scaffold. Further, since interconnectivity between tubal pores is not good enough, efficiency of cell attachment decreases during cell inoculation, and efficiency of transferring essential ingredients for cell attachment and growth, metabolites and cells between pores decreases. Thus, the tubal pores are not suitable for carriers used in tissue engineering, cell culture, and drug delivery.
Accordingly, a method of producing a chitosan scaffold having high tensile strength, uniform size distribution of pores, and excellent interconnectivity between the pores still needs to be developed.